Artificial molar tooth and method of making same



April 10, 1928. 1,665,357

7 A. GYSI ARTIFICIAL MOLAR TOOTH AND METHOD OF MAKING SAME Filed Feb. 21926 4 Sheets- -Sheet 1 [/7 van/0n A/fred G s/I April 10, 1928.1,665,357

A. GYSI ARTIFICIAL MOLAR TOOTH AND METHOD OF MAKING SAME I Filed Feb.26. 1926 4 Sheets-Sheet 2 In yen/0r. /l/fred G /s/I dfforn e y April 10,1928.

A. GYSI ARTIFICIAL MQLAR TOOTH AND METHOD OF MAKING SAME 4 Sheets-Sheet3 Filed Feb. 1926 FIG. 7

v I? veh for.

FIG.8

April 10,1928. 1,665,357

A. GYSI ARTIFICIAL MOLAR TOOTH AND METHOD OF MAKING SAME Filed Feb. 26.1926 4 Sheets-Sheet 4 Patented Apr. 10, 1928.

- UNITED STATES 1,665,357 PATENT OFFICE.

ALFRED GYSL OF ZURICH, SWITZERLAND.

ARTIFICIAL MOLAR 'roo'rn AND METHOD or maxmesm,

Application filed February 28, 1926, Serial 110, 90,726, and in GermanyMarch 14, 1925.

The human mandible, in addition to up and down movements duringmastication, makes the following grinding movements: (1) retrusive; (2)side bites from left to right and from right to left; and (3) incisingor protrusive bite. Besides these three main movements, the mandible canalsomake all movements which are intermediary or between thesemainmovements and are known as intermedlary movements. As

all the back teeth, namely the bicuspids and. -molars, are provided withcusps on their masticating surfaces, these cusps are positioned on thenatural teeth in such a way that they 'do not hinder the above namedmasticating movements. These above named masticating movements do nottake place in a horizontal plane, that, is, not in a plane parallel tothe occlusal plane K, K, (Fig. 7), but really take place in a plane G,G, which has an inclination to the occlusal .plane K, K, offrom 5 to 50to the said occlusal plane. By reason of this, the cusps on all the backteeth have to be limited by facets or defined surfaceswhich have theinclination of the arrows H, H, in Fig. 7, and which are more or lessparallel to the plane G, G, which has the same inclination as theso-ealled condyle path movement of the mandible.

In an ideal natural denture all of the teeth of the lower jaw should bein 'contactwith the corresponding teeth of the upper jaw during themasticating movements. In civilizcd countries, however, where the peopleR subsist mainly upon soft. cooked foods, the

above named ideal conditions can rarely be found because the teeth whichare fixed by their roots in the mandible and in the maxilla can and dostand more or less deviation from the ideal condition without impairingthe masticating function and without loosening the teeth.

When, however, artificial teeth on plates must take the place of thelost natural teeth, it is essential that these artificial teeth shall beso shaped and placedthat substantially all of the teeth of the lowerdenture will contact with the corresponding teeth of the upper dentureduring themasticating movements. It might be assumed that the simplestway to make artificial posterior teeth (bieuspids and molars) would beto copy natural teeth as has been done for many years, and then todepend upon the up and down movement for mastication, but expeingartificial teeth. The natural teeth being firmly fixed in the bone, theyare capable of exerting much greater force than an artifical denturewhich is much less firmly fixed in position, Artificial teeth beingmounted on plates which rest on the mucous membrane, are capable oftransmitting much less masticating force than the natural teeth, andhence should be so constructed that their cutting and grindingcapacities are increased with less power than is available with naturalteeth.

The object of the present invention is to provide forms of teeth withmasticating sur faces that function like the parts of a cutting andgrinding machine, in orderto secure greater masticating efficiency thanis possi-' ble with natural teeth and thereby make up for the loss ofpower due to the way the artificial teeth have to be fixed toandmanipulated' in the mouth.

A further object is to provide a construction which will cause the upperand lower sets of teeth to so cooperate that, when masticating, thecontact of the upper teeth upon the occlusal surfaces of the teeth ofthe lower denture will cause it to be held at all times in position uponthe arch ridge of the lower jaw.

The present invention relates to artificial posterior teeth'which differfrom natural teeth and are constructed in such a way that the abovenamed three main masticatory movements are secured in a technicallyperfeet manner; and, in addition, my artificial teeth containimprovements in operative structure over natural teeth and allartificial teeth which have heretofore been produced prior to myinvention, whereby greater efiiciency in the cutting and grinding ormachine power of the teeth, considered as a chewing or masticatingmachine, is secured.

The form of each posterior tooth in a set of natural teeth differsgreatly from the forms of the adjacent teeth because each tooth dependsfor its masticatory efficiency namely, the eight uppers,,consisting oftwo,

sisting. also of two right and two left" planes or facet surfaces, oneof which planes upon its relation to the adjacent and opposing teeth.Therefore, in order toproperly designposterior teeth, it would beimproper to design each tooth independently, but, 'on the other hand,all the posterior teeth,

right and two left bicuspids, two right and two left molars, and theeight lowers, conbicuspids, two right and two left molars, must "bedesigned as if they were two contiguous units, the upper set of eightteeth constituting one of the operatlve units and the lower set of eightteeth constituting the other operative unit. These two units of eightteeth each must be designed to secure a harmonious relationshi and tofunction together as a cutting an grinding machine. After thesePunitsare made they are each divided into two parts consisting of a lefthalf and a right half, each half containing two bicuspids and" twomolars. Then these four half parts are each subdivided into four partsconsisting of two separate bicuspids and two separate molars. In thisway a set of sixteen single posterior teeth are secured and which may beproperly incorporated into upper and lower dentures which will cooperateand function perfectly.

In the present invention, each posterior tooth is developed from aprimordial form,

the masticating surface of which has at least one obtuse corner which isformedby three unctions with the com lementary planes of the opposingteeth of t e opposite jaw during the retrusive movement ofthe lower jaw,

. another of which planes functions during the protrusive movement, andthe third of which "planes functions during the lateral moveing ruptionsforming cutting edges and the .dif-= fering shapes of the planessecuring greater tool or machine-like efiiciency in cutting andmasticatin food. Theplanes of each of the u per and ower molar teeth andof the lower biscupids form a positive obtuse corner and a negitive ordepressed obtuse corner, the 'posltive and negative corners in eachtooth being out of alinement, but in which further, the positive cornerof either an upper or lower tooth is in alinement with the negativewhich coact with or are comp ementary thus insure movements of themandible. It is here thereto in 'occlusal and masticating relation.

Broadly considered, my invention comprises'the-artificial posteriorteeth embodying the features of improvement above referred to and themethod of making same, all of which are more fully described hereinafterand defined in the claims.

Referring to the accompanying drawings: Fig. 1 is a geometrical diagramillustrating a construction made up of associated parts each having amasticating surface embodying the'primordial form constituting an upperdenture unit containing right and left bicuspids and molars designed tofunction with the lower jaw unit containing complementary right-and leftlower bicuspids and v molars; Fig. 2 is a plan and Fig. 3 a Sectiononline 3-3 of Fig. 2, showing a primordial obtuse positive-corner ofa'form for. use in my improved artificial teeth; Figs. 4 and '5 (sectionon line 5- 5) are similar views in respect to the primordial obtusenegative corners employed in my improved artificial teeth; Fig. 6 showsa portionof Fig. 1 with the outl1ne of the posteriorteeth markedthereon; Fig. -7 i'sa diagram showing the v manner of adapting anarticulator vto' the-- shapingof' the primordial tooth; 'form mas-jticating surfaces illustratedin'Fig. 1 ';'Fig. 8 3 i shows a side viewof one of the cutting knives employed in the articulator; Fig. 9 is afront view of the same; Fig. 10 is a gen-* eral view showing therelative position of the cutting knives when looking -upward upon themwhen positioned on the articulatory Fig. 11 is a primordial form of alower tooth row unit; Fig. 12 is a perspective viewof a primordial formunit of upper teeth; Fig. 13 is a similar view of a corresponding loweror complementary unit; Fig. 14' is a finished right hand view of a lowerunit; Figs. 15 and 15" eating the ocelusal relation of the upper andlower posterior teeth at the right side of the mouth and embodying myimprovements;

are lingual elevations indi- Fig. 16 is a perspective view illustratinga row of the upper posteriors corresponding to the left side of themouth embodying m improvements; Fig. 17 shows the fourteeth illustratedin Fig. 16', somewhat separated and Fig. 18 is a further general view ofthe second upper molar having thereon the addi tional' grooves,fissures, beauty marks, etc. such as inthe commerical teeth. Aprimordial form of an obtuse positive corner is illustrated in Figs. 2and 3 and is geometrically constructed with the three bite guidingplanes or facet surfaces of an upper tooth and ada ted to guidecomplementary planes of'the denture for the lower jaw and the threeprincipal masticating pointed out that Fig. 2 represents a face I corneronthe respective lower or 11 per teeth w Of h P n f h thr e guiding 1 asthey are shown in Fig. 1, the illustration 1n Fig. 2 showing one of theobtuse positive corners which appear in plurality in the illustration ofthe left side of the upper unit but corresponding to the right side ofthe denture when in the mouth. 'In the pa rticus lar illustration ofFigs. 1, 6 and 10, the cut- Itings provide for two bicuspids and threemolars for each side of the jaw, whereas in artificial dentures it iscustomary to employ only two molars on each side, asshown in Figs. 7,11,12 and 13. Y

A primordial form of an obtuse negative or depressed cornergeometrically constructed is shown in Figs. 4' and 5, the latter being asection'of the former on line 55, and said negative corner consists ofthe three bite guiding planes or facet surfaces of a lower tooth and iscomplementary to what is shown in Fig. 2. These negative cornersconstitute the depressions inthe occlusul surfaces of the teeth forcooperation with the cusps of the opposite or coact-i ng teeth andconsequently the teeth of the upper and lower'sets may each have theirocclusal surfaces provided with both positive and negative -corners.

A primordial form of a lower tooth unit from whichfour posterior teethmay be shaped is shown in Fig. 11, andv it is here pointed out that thislower unit is obtained by taking a plaster impression from the upperunit which was made by the action'of the cutting knives arranged in thelower jaw of the articulator, as hereinafter more fully described. Infact, in this invention only the set of molars and bicuspids for one ofthe jaws are modeled b use of the cutting knives, as indicated in lmordial tooth form for the other jaw is made by molding or casting thesame from the cut form so that the teeth of one jaw are complementary tothe teeth of the other jaw, and this is true irrespective of whether thecutprimordial form is'made for the upper or for the lower set of teeth.

The right side of Fig. 12 shows the mechanical primordial constructionfollowing the essentials of the geometrical design of Fig. 1, whereasthe left side of the figure shows a similar construction from which all.of the superfluous material has been removed, leaving the Bicuspid andmolar teeth which contained the bite guiding planes or facet surfaces intheir natural outline upon the occlusal'surfaces.

Fig 13 is a corresponding lower .1 or complementary unit with theocclusal surfaces inversely formed to those shown in Fig. 12, just aswould occur by casting or molding it from the structure of Fig. 12 as apattern' On the right hand side, the material has been cut away to showclearly the shape of the two molars and two bicuspids, whereas on theleft hand side of the primordial form, the general position and shapesof as 15 in the instance described.

ig. 7, and the priside bite angle of theteeth, by reason of whichrotation centers, the axis for the normal side bite movement to the leftand to the right, can be geometrically determined. The centers R hearsuch a relation to the position of the condyles g, 1, that the upperarticulator frame is permitted to move in the directions according tothe curved lines 4, 4, in Fig. 1. The connecting lines between thepoints C, R, in Fig. 1, form generallyan angle alpha.with the connectingline between the two condyles. may vary between 5 and 30 and is shown InFig. 7,

the angle beta is shown as set at 33,but

' where an adjustable articulator isemployed, this angle may be varied,that is to say, it

may be. reater or smaller. These angles, alpha? and'beta, are not variedfor each individual case, but are predetermined, preferably asaforesaid. as a basis for producing primordial form units to correspondto required teeth forms for general use to be produced having myimproved mast1catmg or occlusal-surfaces suitable for proper ac? tionwith maxilla and mandible of sizes and' shapes and condyle and. tcmporomandibular articulations corresponding to a natural skull. The points C,C, J,,in Fig. 1, are the three main points of the equilateral triangleof the mandible, J being the point where the two (upperand lower)central incisors meet, otherwise indicated at 2 in Fig. 7. The points M,M, F, are the centers by which the natural are 3, 3 and 3, of the toothrows can be constructed and by using the two points L, L, successivelyas centers for the compass,

the equallyspaced arcs 6, 6, corresponding [to the grooves of the upperbicus pids. and

molar teeth' may be drawn, and by next placing thecompass at the pointF, the arc 3 of the curve of. the anterior, teeth may be drawn. .Also,by placing the compass successively at the center points R, R,concentric arcs 4' are drawn from each of said centers, startingapproximately from the centers M, M, and twenty of these arcs arerespectively grouped into ten are sections Z of increasing widths andspaces, determined in the manner hereinafter described. The radialdistances Z of the 'arcs 4 are dctcrmincd as follows: Referring to Fig.7, and keeping in mind the radial lines with the arrow marks leading to'the point P at the front of the This angle III movable frame of thearticulator which gives the vertical angles of the cutting edges ofthe-knives 16 and also keeping in mind the lines H parallel to thecondyle socket line G also formed by the part on the upper or movableframe of guide portion 12 at the front. of the base or stationary partof the; articulator over which the pin 14 travels; we will find that thesaid parallel lines H intersect the radial lines leading from the pointP at what would be the-apex of one of the positive corners of cusps ofthe upper teeth, as very clearly shown in Fig. 7. If now 'we draw radiallines from the point Kto these ntersecting points of the parallel andradial lines above mentioned, we will obtain dis tances between theseradiahlines from the point K measured along an arc B, B, also struckfrom the center K and passing through the highest points 17 of the cuteting knives 16,-which distances will repre? sent the radial distances Zin the diagram Fig; 1. As stated, the point K corresponds, to theaverage arc of a natural row of teeth with a radius of about 15 to 20centimeters, (page 12, line 20). It is to be understood that thedistances and angles between the operative parts of the articulator areal ready determinedin the commercial articulators by giving tothemaverage distances and angles based upon investigation of natural skulls.After drawing the tooth are or arch 3 from right center M and the arcs 4from the left center R, the equi-spaced arcs 6 from the right centerLinay be drawn between the left hand arcs 4 in pairs (Z) ,and close tothe tooth are 3, ,giving intersecting points 5. These are portions 6give the position of the knives 16 in Fig. 7. Then the arcs 4 from theright center R are drawn through the intersecting points 5. In practice,when the knives 16 have been positioned in thearticulator and thearticulators parts given the relative movements, such as occur inmastication, the points 17 thereof cut or scrape the grooves in theplaster corresponding to the negative corners 8 lyingin arcs 6 andindirectly form the positive corner 7 by the'cooperation' of the twoadjacent knives. While the short are. per- I tions 6 between the arcs 4'in pairs may be 1ncentric arcs equally spaced apartgsai dividuallyconsidered as straight lines,-they would be tangential to the arcs 6.The center L for these arcs 6 may be ositioned as follows: Thiscenter Lwill lie in a horizontal line (from L to L) across'the rear. ends of thesecond or posterior. molars. .(whereat thecutting knives 16 on the rightand left sides of the denture are parallel) and where a tangent from.the uppermost are 4 crosses it,-..-the tangent beginning adjacent to thetooth row are 3; and the arcs 6 described about said center L aresubstantial]; conthe 'articulator and the ing predetermined for thewidth to be pro: I k

= vided for in V sidered. Having once. positioned the knives,

the tooth buccal-lingually con-. I A

they, by reason of the possible movements 8 of't e same formationlim tedby three planes or facet surfaces 9, 10, and, 11, as

'70 cutting or carving of the plaster to the de- 1 of. the drawings. In

{and negative or depressed corners graphically illustrated in Figs.2.to-5. The

design matically in the plaster when the knives '16 are set as describedhereinafter in connection wih. Figs. 1, 7, 8, 9, and 10, and the uppermovable frame ofthe articulator carrycorners 7 (cusps) (Figs-2 and'3)..are formed as 'well as the negative or depressed corners 8correspondingto the depressions in the teeth. The various arcs 4, 4, and6, 6, are

-definitely positioned on thediagram as explained, and as these are all:definitely-deterof'rthe relief is produced auto-- the plaster is movedover the knives in the various directions permitted by the ar-vticulator; and in Fig; '1, this relief -is indicated by the shadingwhereby the positive.

mined by the inoyable points'of the: artic u-' lator and the angle,shape and positionsjof the cutters 16, the final design in the reliefproduced' bythe cutters is "caused, to have a form in which thevariousfacets 9, 10 and 11 lie in planesat apart (Figs. 2 and 3 4negative corners. The shading on Fig. 1 and on others of the figuresismerely to indicate the different portions in the actual whether theyform' positive corners or relief in plaster and whose defining lines areformed by theeorresponding' arcs 4. and

' 6, as explained.

The general sizes of the teeth to be formed are roug ly laid out, asinFig. 7, the'cutting points 17 of theknives are definitely positioned inthe arc B, B, which is also a predetermined are for the occlusalsurface. These cutting points where they lie in the no I predeterminedby the dentist and when are B, B, are' then connected by the obliqueradial lines with arrow heads from the com mon center P, this will givethe radial angles which definitely :give the angle of the anteriorfacets 11. of the teeth and thereafter I lines H parallel tot he line G,G, (through the condyle) and extending through the points 17 of theteeth gives the obliquityof these:parallel lines and form the. angle ofthe posterior facets 9 of the teeth. 7

It is to be understood that the arcs the right handcenter R are notcontinued from the right hand side across the center of the'diagram intothe left hand side, but that 4 froni" hand arcs 4 and 6 and, t erefore,these left that in Fig.7, the tooth hand arcs crossing the points 5described from the right hand center R will be formed from all thecrossing points 5 without regard to the position of the arcs 4 at theright hand side. In regard to the choosing of the points 5 as to whichshall form parts of the positive or negative corners it will be notedfacets have high and low "points alternately and, therefore, the points17 would represent the points 5 on the upper arcs 4 of each pair whilethe intermediate depressed points would correspond to the points 5 whichwould be formed by the crossing of the are 6 with the lower arcs 4 ofeach of the pairs. The direction of the arcs 6 indicates the positioningof the knives 16 as shown in F i and thepoints 17 of these knives won (1be located at one of the .intersecting points 5 and which would, in itsoperation upon the plaster, cut one of the depressed corners.

The distance apart of the arcs 6 is uniform, and this distance isselected in respect to the width of the teeth in a lingualbuccaldirection and to provide the necessary I number of facets to form atooth structure of normal width. It will be understood that for a smalljaw the widths will be less than for a large jaw. The distance apart ofthe concentric arcs 6 is predetermined to suit the widths of the toothstructures to be made. c y

The oblique arcs from the right hand center R do not bear any relationto the right hand arcs 4, except that they are made from the samecenter. They are positioned to pass through the points 5 at the lefthand side without any regard to the arcs 4 at the right hand side ofFig. 1, and consequently the are not arranged with that uniformity whichis peculiar to the paired arcs 4 at each side of the diagram Fig. 1 inconnection with the letters Z.

The three planes or facet surfaces of each corner 7 and 8 are theguiding surfaces of the teeth during the masticating movement. In thepreferred form of obtuse corners adapted to my invention of artificialteeth, the corners are best made in a manner similar to one of thecorners of a rhombic-dodecahedron'or a pentagon-dodecahedron, in whichthe angles between .the ridges or junctions of the planes or facetsurfaces 9, 10 and 11, are 110- taken in the plane of said surfaces, asindicated in Fig. 2, such corners, constituting essentials to themasticating surfaces of the teeth, are best suited for the naturalmovements of the jaw in biting and masticating. The facet surfaces 9(Figs. 1 and 12, for example) are the guiding surfaces of the'teethduring the protruslve or incising bite. The facet surfaces 10 are theguiding surfaces dur- "teeth, a mirror picture or inverse view of theupper *relief A is taken by a cast therefrom.

A relief A taken as a primordial form with its positive and negativeobtuse corners and their three guiding planes or facet surfaces 9, 10and 11, maybe made according to the geometrical construction shown inFig. 1, in any plastic material such as wax, plaster, etc., by asculptoring process to serve as the model for an upper set of teeth asindicated in Fig. 6, and outlined at 25, the unit teeth in this figurehaving the primordial masticating surfaces which are preserved intact,although by hand carving the corners can be slightly rounded, additionalcurves, fissures, beauty marks, etc., added, to constitute a tooth model(Fig. 14), following which, in shape and design, the correspondingporcelain teeth may be made.

The unit containing an upper set of teeth as outline 25 being themodelfor a single tooth.

In Fig. 1, the primordial form is shown-for I an up er set of posteriorteeth, but in Fig. 6' one alf or oneunit is shown by way of illustrationwhen outlining the teeth at 25. Fig. 6 illustrates how the upper rightposterior teeth can be isolated 1n their natural outline from thegeometrically constructed unit shown in Fig. 1, by a rocess of cuttingaway of the surplusmaterial (not shaded). In Fig. 6 the tooth outlinesdenoted by 10, 10 and 10 and the next upper outline there to denoted by25, represent. the four posterior teeth, as shown by themselves in Fi s.16 and 17. The principle involved in this 1nvention will apply inproducing the required angles and facet shapes for the whole pos siblesixteen teeth of the upper jaw, but as a commercial proposition, t iscustomary to make four posterior teeth, namely, two bicuspids and twomolars for each side of the denture by this method and form the othersix frontal teeth more for artistic appearance since they have nodepressions assorocess would indicate the required shapes or the wholesixteen teeth in the upper jaw,

and Fig. 7 shows the making of five teeth on each side. y

The making of a relief according to the design of Fig.1 can be easilydone by a simple mechanical procedure with the ald of an I articulator.For this purpose, I use any I good; articulator, such as the articulatordescribed in my ;German Patent No.'293,074,

i articulator Fig.

7 thereof. 1 secure upon the lower frame of I that the points 17 of thethe articulator a double row of cutting knives in the shape of sharksteeth 16, Fig. 7 and Fig. 10, which knives correspond to the negativecorners 8 (Fig. 1) in such a way knives 16 shown in Fig. 10 coincidewith the recesses or negative corners 8. In Fi lOis shown a general-viewof the relative ositions of these cuttingkniveswhen' looking upward uponthem, and the points'at the end of the heavy black marks 17' re resentthe points of the cutting knives w ich are arranged in a schematic reroduction of Fig. 1. In shape the knives i 8 and Fig.- 9) have parallelsides 18 and t e cutting edges thereof are oppositely beveled and thefront end is per pendicular. .The cutting edges 19, in plan, arearranged in the directions of the arcs 6 described from the centers L,L, Fig. 1.

. The points 17 of the knives are also preferably arranged in a concavearc B, de-. scribed from center K (Fig. 7 which corresponds to theaverage arc of a natural row of teeth with a radius of about 15 or 20centimeters. The cutting edges 19- are directed Y towards the commoncenter P which is about one centimeter in front of thepoint of the nose21, said center being also determined on the articulator' (Fig. 7) bythe point'P. This new .form of cutting knife makes it possible tomechanically produce a model of the upper tooth row. If in the upperpartof the articulatora-block of plaster 22,Fig. 12, is fixed, and if itis moved upon thecutting knives by making side bite movement to theright side and to the left side, protrusive movements forward and backward and all intermediary movements (in an anatomically correctarticulator), the plas- Lter block will become out into the form ofreliefi-shown by'Fg. 1 with its positive and" negative corners-A',and ascan be seen 12 and as also on the right side of .Fi

hand side where shown in Fig. 12 at thev ie the unnecessary portions ofthe plaster on both sides of the row of teeth have been cut away,whereby insteadof three series of corners (7 and 8), asshownin Fig. 1,only two series of corners remain in Fig. 12. But, in Fig. 12 can stillbe seen the positive corners 7 and the negativecorners 8, each of whichis formed. by the three planes 9, 10

and 11. If we draw on the relief of the lower tooth row Fig. 13, theprolongations ofthe ridges as at 23- in Fig. 11 of the correspondingplanes, then this relief can be compared with a double row of rods orpiles of rectangular cross section projecting vary- 1,ces,s57

ing distances from the corresponding to one side of the block having'theappearance of being inclined downward and inward in the same generaldirection. In Fig. 1, the corresponding double row of rectangular planesor facets 11- of opposite tooth rowsare inclined" toward a (ommon medianline above the figure. These side of the figure region these planes 24are interrupted alter nately, one plane extending across the tooth andthe next plane being interrupted as, at 24*. It is also importantthat,the planes 11') on the right side of Fig. 12 and which. guide theside bite movement are differently shaped and not continuous with eachother. This non-continuity is shown in Fig. 6 at 10', 10 10 and 10, andin Fig. 12 at 10 and 10; By this non-continuity, ridges are formed thatact? as cutting edges and which increase the tool or machine-like actionof the masticating surfaces so that the effective masticating power mayapproximate the masticating power of in the bone.

In Fig. 12, right side of the figure representing. the upper tooth row(inverted) and in Fig. 13

at the left side is shown the relief of the corresponding lower toothrow, the same therefrom. The portion of the plaster material notrequired for theformation ofthe teeth, that is,-the material outside ofthe 12 and in thev right side of Fig. 13.' These constitutetheprimordial forms of the teeth. his .now necessary to carve the outlines,

natural teeth that are rigid loo the relief illustrated on the base, allof the rods shown a series of 'being a cast counter or impression takendeepen the grooves and round off the corners.

so that the teeth will present a more natural appearance, with theresult shown in Fig.- 14, 1n which is shown a series of depressions i 26made in the mastic'ating surfaces for the purpose of facilitating thecrushing of food and which may also be used for identifying therespective teeth. In the first bicuspid bicuspid two depressions mayappear. In

one depression only appears. In the second the first molar onedepression only appears, while in the second molar two depressionsappear. the planes or' facet surfaces, but they reduce the area ofthe-planes or facet surfaces and These depressions do not destroy fincrease the cutting power of the teeth. I For the purpose ofsecuring'greater'm-astieating efiiciency, the lingual cusp 28 of thesecond upper bicuspid tooth is formed so that when it is articulatedwith the corresponding lower bicuspid and first molar tooth it alsoengages the masticating surface at 8 of the second lower bicuspidinstead of only projecting between the second lower bicuspid and thefirst molar, as occurs on the buccal sidev wherein the buccal cusp 27 ofthe upper second bicuspid tooth does project in o the inter-dental spacebetween the second lower bicuspid and the first lower molar '(Fig. In myimproved. teeth,

the lingual cusp of the first upper bicuspid 0nd lower bicuspids, asheretofore.

is also formed so that it similarly engages the masticatory surfaces ofthe first lower bicuspid instead of projecting into the-interdentalspace between thefirst and second lower bicuspids, whereas the buccalcusp of the upper first bicuspid does project into the inter-dentalspace between the first and sec- This construction ofthe bicuspidsproviding increased masticating capacity is shown in Figs. 15 and 15, inwhich it will be observed that the lingual cusps of the upper bicuspidsY and Z are respectively received in depressed corners 8 in the uppersurfaces of the lower bicuspids -Y and Z, and it will further be notedthat the oblique planes or facets of the upperbicuspid Y cooperates withthe complementary planes on the lower bicuspid Y and first lower molarX, whereas the upper first bicuspid Z has its planes .or facetscomplementary to and cooperating only with planes or facets onboth thelower bicuspids Y and Z. To insure this co action at 8 between theocclusal surfaces of the upper and lower bicuspids, it is necessary thatthe lingual sides of the lower bicuspids are provided with the cornersor depressions 8 to the rear of these lingual cusps and for the upperbicuspids Y and Z to be given, as it were, a horizontal twist 7 so thatthe lingual cusps are advanced relatively to the buccal cusps wherebytheformer engage the masticating surfaces of the depressions in the lowerbicuspids. In this manner, the bicuspids coact to insure improvedmasticatory action.

In respect to the lower bicuspid teeth X and Y having three cusps asindicated at 8 in Figs. 13 and 15", it is. pointed out that'as aboveexplained these bicuspidsj ave the depressed corners 8 and [from theexplanations as to the same being formed by the three planes 9, 10 and11 at an angle to each other and the .further fact that the generalocclusal surface is more or less circular, it will necessarily resultthat the said planes project to form three cusps about the depressedcorner 8, and the shapes and extent of the cusps varying in shapeaccording to the outside configuration of the final tooth form and theposition of the depressed corner awayfrom the'center of the occlusalsurface. In the present case, these depressions are considerably awayfrom the center and hence they ditfer'in-size.

After the tooth models have been prebiscuitedduplicates of the models inporce lain material and whichare subsequently vitrified.r Theseartificial teeth may be produced as an .integral structure comprising aunit of four teeth or separate units for the two molars and for the twobicuspids, or, on the other hand, each tooth may be molded separately asindicated in F ig.-17, in which the two molars (V and X and twobicuspids Y and Z-of the upper set are indicated in theirrelativepositions but separated interdentally to' illustrate theirindependence. Furthermore, the illustration of the individualteeth inFig. 1-7 and the correlation of these teeth when properly positioned, asindicated in Figs. 15 and 16,.will' make the fundamentalfeaturesembodying the corners and planes of the upper set more clearlyunderstood; and reference to Fig. 18, which shows the finished porcelaintooth corresponding to therear -molar X, will give a betterunderstanding of the commercial tooth when the 1 curves, fissures,beauty marks, etc, have been applied to it, withoutdestroying thecooperating planes or facets, and compares with the rear lower molar'ofFig. 14- which would cooperate with it when in occlusal relation, asindi cated in Fig. 15.: As the lower posterior teeth have their occlusalsurfaces formed complementary to the occlusal surfaces of the upperteeth, it willnot be necessary to illustrate them more in detail than isfound in Figs. 11, 13,14 and '15, but they, as in the case ,of theupperteeth, maybe formed in blocks of two or four or as individualteeth,'as desired. f

I have described my improved method and the article of manufactureproduced thereby in connection with apparatus which I deem to be bestsuited to the requirements of'the invention and on account .of economyis preferred-in commercial practice-but I do not restrict onconfinemyself" to the minor or secondarydetails either as to the method ofprocedureor the means employed .in putting; it into eifect,asvariations, therein maybe resorted to as matters for the skilledartisan" and without a departure from the spirit of the invention.

Having now described my invention, whatI claim and desire to secure byLetters Patent is:

1. Themethod for the mechanical pror 1 ing the primordial duction ofprimordial forms of the back teeth to constitute a portion of anartificial denture, which consists insecuring to one member of anarticulator two rows of cutting knives arranged in a curve correspondingto a natural back tooth row at one side of the jaw and in more or lessparallel relation and having cutting edges which slope backward anddownward with a gradual lessening obliquity from front to rear, applyingplaster to the other member of the -a1'ticulator,and thereafter causinga relative movement between the knives and the laster corresponding tothe left and to the right side bite movements and to the forward orprotrusive movement and backward or retrusive movement and to allpossible movements of the articulator corresponding .to intermediarymasticatory d1- rections so that angular depression and elevations eachformed of three planes inclined to each other are cut in and upon theplaster block and which then serve as the primordial form ofthematicatory surfaces of the back tooth row.

2. The method according -to claim 1, wherein further, from the plasterblock havmasticatory surface cut thereinpa second block of plaster. orits equivalent is produced by casting or molding it from the primordialform and having inverse elevations and depressions, one of said plasterblocks shaped to represent the masticatory surfaces of the back teethcorresponding to v the tooth row'of one of the jaws and the other ofsaid plaster blocks shaped wherein further,

faces of the .back

represent the masticatory surfaces of the back teeth corresponding tothose of the other jaw.

3. The method according to claim 1,

from the plaster block having the primordial form of the tooth row cuttherein, a second block of plaster or its equivalent'is cast or moldedtherefromnnd having inverse elevations'and depressions, one of saidplaster blocks shaped to represent the masticatory surfaces of the backteeth corresponding to those-of one of the jaws, and the other of saidplaster blocks shaped .to' represent the mastlcatory surteethcorresponding to those of the other jaw, and further characterized, byfinally cuttingaway the sur plus plaster material and dividing the toothrow block transversely into sections corresponding to the severalback-teeth eaclraccording to its required occlusal or masticas torysurface structure.

4. Back teeth for part of an artifical denture, wherein each tooth isprovided with at least one obtuse corner on its masticatlng surfaceshaped according to form which is characterized so that each of thesecorners is formed by three incline form of the tooth .row-

corners and facet of substantially the same inclination as @thetransverse plane I facet lying in a plane corresponding to the areadvanced wherebya primord al planes 9, 10 and 11,, respectively arrangedat angles to each other, one of which planes 9 is inclined in a forwardand backward direction and extends in widthgbuccal-lingually and servesas a sliding and guiding surface for the teeth in the opposite jawduring the protrusive or iricisingbite movement, another of which planes10 is inclined in a buccal-lingual direction so as to serve. as aguiding surface during the side bite movement of the jaw, and thethirdof which planes 11 is inclined in a forward and backward" directionso'as to serve as a guiding surface during the retrusive movement.

' 5. A row of upper hack teeth as part of an artitical denture havingtheir mastication surface provided with facets lying in a plurality ofplanes having different inclinations and three of which planes ofdifferent inclinations form obtuse corners of. cusps and likewise threeof the planes of different inclination form depressions of the samegeneral shape, each of the teeth having one' of their facets arranged ina plane corresponding to one-of the inclinations and extending inwidthtransversely across the teeth in a buccal-lingua'l direction, andfurther, said teeth each having twoother facets separated by thetransverse facet and lying in the oblique planes corresponding to one ofthe other inclinations and obliquely presented to the buccal side of theteeth, and in which also, the molar teeth are each provided with anupward corner or cusp at the junction of their anterior and buccalformed by a shorttransverse first mentioned and a third and remainingplane inclination.

6. The invention according to clann 5,

-wherein further, a corresponding set of lower back teeth constituting acooperating part of a lower artitical denture is provided having facets,and deperssions complem'em tary to'the depressions and facets of theupper set of back teeth, and in which further, the lower bicuspids areprovided with on the depressions V buccal and lingual cusps, and

to the main lingual side infadditionthe upper hicuspids are eachprovided with two ma n cusps 111' whlch. the lingual cusps pressions inthe corresponding lower bicuspids while the buccal cusps of said upperthe inter-dental space bebicuspids occupy teeth with which they enbuccalcusps, and lowerhicuspids are prod vided for a lower denture having-ontheir that the lin-' 'gual cusps are advanced relatively to the they.engage the de- 1 lingual sides two cusps and a depression between them,and whereby said lingual cusps of the upper bicuspids occupy a. positionto be received in depressions in the adjacent lower bicuspids instead ofwholly occupying the interdental space between the corresponding lowerteeth.

8. An artificial molar tooth having facets on its masticating areaformed of a plurality of surfaces arranged in inclined planes abuttingin sets of three planes when arranged at an angle to each other, two ofwhich facets extend in a buccal-lingual direction of the tooth, oneentirely across the tooth and the other partway only, and the surfacesof the other facets forming parts of inclined planes arranged in adirection from the posterior to the anterior parts of the tooth, saidplanes forming at least six facets arranged inpairs at an angle to eachother and said latter planes interrupted in a posterior-anteriordirection by'the buccallingual planes. 1

9. An artificial molar tooth having facets on its masticating surfaceformed of a plurality of smaller surfaces arranged in planes at an angleto each other, two of which facets extend in a buccal-lingual direction,one entirely across the tooth and the other partway only of the tooth,and the remaining facets extending in a direction from the posterior tothe anterior parts of the tooth and arranged in pairs at an angle toeach other and in planes which are interrupted by the buccal-lingualplane of the first mentioned facets.

10. An upper bicuspid for an artificial denture, in which there is alongitudinal main groove and a buccal cusp and a lingual cusp onopposite sides of the main groove, and wherein further, the lingual cuspis advanced beyond the position of the buccal cusp whereby thealineinent between the two cusps is greatly oblique to the ahnement ofthe main longitudinal groove and as though the lingual cusp of the toothwas given a horizontal twist.

11. A lower bicuspid for an artificial denture, in which the buccal sideis provided with a single cusp and the lingual side is providedwith ananterior large cusp and a posterior small cusp with a depression.between them and the buccal cusp for receiving the lingual cusp of anupper bicuspid.

12. The invention according to claim 11, wherein further, the depressionis formed by three oblique facets lying in corresponding oblique planesmaking equal angles with each other and located near the posterior sideof the occlusal surface of the tooth.

13. A row of upper back teeth, including molars and bicuspids as part ofan artificial denture, having their mastication surface provided withfacets lying in a plurality of planes having inclinations in or parallelto three main planes and in which three of said facets of differentinclinations when associated together in one relation form positivecorners or cusps and likewise in association in another relation formnegative corners or depressions of the same general shape, each of theteeth having one of its facets arranged in a plane corresponding to oneof the main plane inclinations and extending in width transverselyacross the tooth in a lingual-buccal direction, and further, said teethalso having facets obliquely presented to the buccal side of the toothand having an inclination corresponding to another of the main planeinclinations,

and in which also the molar teeth have their facets respectivelyseparated into parts in a mesio-distal direction by the transverse facetportions and facets and respectively lying in oblique planes whichareeach coincident with one of the two other main plane inclinations andalso each molar provided with a corner or cusp atthe junction of theiranterior and buccal walls formed by short transverse facets and theformer having substantially the same inclination as the' transverseplane and facet first mentioned.

14. An artificial molar tooth having facets on its mastication area,said facets constituting a plurality of inclined surfaces respectivelyarranged in abutting relation in sets of three planes, said planesarranged at an angle to each other to form positive cor ners or cuspsand negative depressed corners two of which facets of one inclinationextending in a buccal-lingual direction of the tooth, one entirelyacross the tooth and the other part way only, and the surfaces of theother facets forming parts of the inclined planes arrangeddisconnectedly in a direction from the posterior to the anteriorportions of the tooth by the buccal-lingual facets and forming at leastsix facets arranged in pairs at an angle to each other.

In testimony of which invention, 1 hercunto set my hand.

ALFRED G Y S1.

